1. Field of the Invention
The present invention relates to a synchronous control device verifying the synchronous relationship in machinery such as machine tools and industrial machinery, in devices, and in equipment which have a plurality of movable axes driven by servo-motors, and in which these movable axes are synchronized.
2. Description of the Related Art
In some cases, machine tools and industrial machinery have a plurality of movable axes (axes driving movable parts), and this plurality of movable axes operate in a coordinated manner. For example, when cutting a moving workpiece with a cutter at the prescribed position, it is necessary to maintain the synchronous relationship between the movable axis driving the workpiece and the movable axis driving the cutter from start to completion of cutting, however, this synchronization need not be maintained during other intervals. Thus, it is necessary to check the synchronous relationship during the interval in which it is necessary to maintain the synchronous relationship between the plurality of movable axes.
Conventionally, checks are conducted to determine whether the value of position deviation (or the value of delay with respect to a command for each movable axis) has exceeded the maximum value, in other words, whether each movable axis is operating in accordance with the command, in order to check the synchronous relationship between this plurality of movable axes.
The conventional check of the synchronous relationship by checking position deviation is a check to determine whether or not each movable axis is operating in accordance with the command, and is an individual check. When the command itself contains an error due to a mistake in programming and the like, each movable axis operates according to the command, however there is a problem in that, if the synchronous relationship breaks down, the synchronous relationship can no longer be checked.
Furthermore, since the position deviation indicates the deviation with respect to the command, an alarm is generated and the program is stopped when the normal maximum value is exceeded, generally, and there is a problem in that avoidance operation and the like cannot be executed immediately.